JPH06279326A - Production of 2,6-dimethylnaphthalene - Google Patents

Abstract

PURPOSE:To industrially obtain 2,6-dimethylnaphthalene (DMN) in a high efficiency by suppressing the formation of isomers hard to isomerize to the other groups in trans-alkylation process. CONSTITUTION:Naphthalene (NF) and/or monomethylnaphthalene (MMN) is transalkylated by a polyalkylbenzene in the presence of pentasil-type zeolite at a conversion rate defined by the formula (A and B are sums of molar fraction for the NF and MMN in the naphthalene compounds in the raw material(s) and products, respectively) of <=30%, thus producing dimethylnaphthalenes (DMN). The resultant reaction mixture is then separated into (l) unreusable polyalkylbenzenes, (2) reusable polyalkylbenzenes (unreacted), (3) unreacted NF and/or MMN and (4) DMNs. 2,6-DMN is separated from the fraction 4. The DMNs after separation of 2,6-DMN are isomerized to convert the isomers belonging to 2,6-DMN group and 2,7-DMN group into 2,6-DMN.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for industrially and efficiently producing 2,6-dimethylnaphthalene from naphthalene or monomethylnaphthalene as a raw material.

[0002]

Technical background 2,6-dimethylnaphthalene (hereinafter,
"2,6-DMN" is abbreviated, and dimethylnaphthalene is also abbreviated as "DMN" in accordance with this), when a side chain methyl group is oxidized, it is an industrially important compound naphthalene-
2,6-Dicarboxylic acid (hereinafter, abbreviated as "2,6-NDCA") is given, and from the polyester obtained by using the 2,6-NDCA as a raw material, excellent quality synthetic fibers, films and the like can be obtained.

As a study on a method for producing 2,6-DMN, a method for producing DMN contained in coal dry distillation oil or FCC light cycle oil by crystallization separation or complex extraction separation (Japanese Patent Publication No. 47-44729, USP3). , 69
No. 7,414) or a synthetic method using orthoxylene and butadiene as raw materials by alkenylation → cyclization → dehydrogenation → isomerization → crystallization separation (WOP 91/16,
284, JP-A-48-61461, USP 3,244,
758) has been proposed.

However, only the above separation causes 2,6-DMN.
The technique for obtaining the above method is not an economical method because it has a problem that a large amount of the raw material is required because the concentration of 2,6-DMN in the raw material is generally low. Although the method for producing 2,6-DMN by the above-mentioned alkenylation reaction is an efficient production method, it is expensive and dangerous in the alkenylation step, which is an important step with many steps. There are problems such as the need to use high alkali metals as catalysts, and industrialization has not yet been achieved.

Furthermore, recently, a method of methylating naphthalene or monomethylnaphthalene with methanol to obtain DMN, or a method of transmethylating naphthalene or monomethylnaphthalene with polymethylbenzene to obtain methylnaphthalene or dimethylnaphthalene (Japanese Patent Laid-Open No. 266834/1992). 63-1473
7, JP-A-60-45536).
These are 2,6-
DMN is attractive in that it can be produced, but 9 kinds of DM other than trimethylbenzene and 2,6-DMN
The production of N is unavoidable, these by-products are of little industrial value and the treatment of by-products is a problem of this process.

The isomerization technique of DMNs can be said to be an important technique for solving these problems. As the isomerization technique, a method of producing 2,6-DMN by isomerizing DMN after separating 2,6-DMN (USP 4,55
6,751, JP-A-60-94926, JP-A-60-6.
9043, JP-A-60-69042, JP-A-59-68
433 and Japanese Patent Laid-Open No. 58-210031). Furthermore, isomerization is incorporated as an important step, and the steps of alkylation, disproportionation, transmethylation, isomerization, distillation separation, and separation of 2,6-DMN are combined into a total process 2,6- DMN production method (JP-A-4-1142, JP-A-4-13637, JP-A-4-4)
9252, JP-A-4-74142, JP-A-4-1128
39) are also proposed.

However, in these methods, the efficiency in the conversion technology by a catalyst such as isomerization or alkylation (disproportionation, transalkylation), which is the most important step, has not been clarified. In a similar examination by
In many cases, unsatisfactory results are shown in terms of selectivity to 2,6-DMN, combination of reactors, and catalyst life. Especially 2,
The isomerization reaction from the 3-DMN group to other DMN groups is difficult, and no solution to this point has been clarified in any of the proposals, and it is difficult to say that this is a practical manufacturing process. Further, the 2,3-DMN group and the 1,2-DMN group have lower reactivity of the isomerization reaction to the outside of the group as compared with other dimethylnaphthalenes, and in the above combination process, the isomerization reaction of the dimethylnaphthalene group and the dimethylnaphthalene group may not be performed during the process. It is highly possible that compounds accumulate, and unless these problems are solved, practical application of these processes is impossible. Details of these DMN groups will be shown in Chemical Formula 1 below.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above problems,
Using naphthalene and monomethylnaphthalene as raw materials,
The present invention provides a method for industrially and efficiently producing 2,6-DMN.

[0009]

SUMMARY OF THE INVENTION The method for producing 2,6-DMN of the present invention comprises: [1] naphthalene, monomethylnaphthalene or a mixture thereof as a raw material, and the number of the raw materials is adjusted by polyalkylbenzene in the presence of pentasil-type zeolite. A first step of producing a dimethylnaphthalene compound by transalkylation at a molar conversion rate represented by the formula 2 of 30% or less (that is, “transalkylation step”),

[2] The second step of separating the reaction mixture of the first step into four fractions of non-reusable polyalkylbenzene, reusable polyalkylbenzene, unreacted naphthalene, monomethylnaphthalene and dimethylnaphthalene (that is, , "Separation step"), [3] Third separation of 2,6-dimethylnaphthalene from dimethylnaphthalenes of the fraction separated in the second step
Step (namely, "separation and purification step of 2,6-DMN"), and [4] 2,6-dimethylnaphthalene is isomerized by isomerizing dimethylnaphthalene after separating 2,6-dimethylnaphthalene in the third step. Is manufactured by the fourth step (ie, "isomerization step").

[0011]

[Equation 2]

According to the present invention, in the transalkylation step of the first step, the molar conversion of the raw material naphthalene or monomethylnaphthalene or a mixture thereof (hereinafter, these may be collectively referred to as “naphthalene”) ( That is, by controlling the transalkylation ratio of the raw material naphthalene to 30% or less, the 2,3-DMN group (2,3,3) having a low conversion efficiency to 2,6-DMN in the isomerization step of the fourth step is obtained. -DMN, 1,3-D
MN and 1,4-DMN) and 1,2-DMN production is low. That is, DMN
Is classified into the group shown in Chemical formula 1 due to the difficulty of conversion between isomers. In the present invention, among these groups, the generation of 2,6-DMN and a group that is easily converted into the 2,6-DMN is promoted, and the generation of a group that is difficult to be converted into 2,6-DMN is suppressed. As a result, 2,6-DMN is produced with high efficiency.

[0013]

[Chemical 1]

The arrow in Chemical formula 1 indicates the case where an isomerization reaction occurs. As shown by the arrow in Chemical formula 1, the isomerization reaction within each group is very likely to occur. However, the isomerization reaction between each group is difficult (Fri
es rule). However, when a pentasil-type zeolite is used as a catalyst, the conversion between the 2,6-DMN group and the 2,7-DMN group occurs relatively easily as shown by the arrow in Chemical formula 1.

The above-mentioned mutual relationship between DMN isomers is important for the present invention, and DMNs are 2,6-DM.
It is divided into a compound group in which it is easy to interconvert the 2,7-DMN group with the N group, and a compound group in which it is difficult to interconvert into other groups such as the 2,3-DMN group and the 1,2-DMN group. be able to.

If only the 2,6-DMN group and the 2,7-DMN group can be produced in the transalkylation step of the first step, the isomerization step of the fourth step can be repeated several times. Thus, it becomes possible to convert all of the raw material naphthalene compounds into the desired 2,6-DMN. On the other hand, in the transalkylation step of the first step, 2,3-DMN group and 1,2-DMN group
When a large amount of N is generated, 2,6-DMN is carried out of the process, so that the 2,3-DMN group and 1,2-DMN are accumulated in the process by recycling the feed. . This indicates that this manufacturing process itself does not hold.

The present invention solves this problem in the transalkylation step by (1) using a pentasil-type zeolite having shape selectivity as a catalyst, and (2) methanol which is generally used as an alkylating agent as an alkylating agent. By using polyanoxybenzene, which has a larger molecular size than that of the catalyst and the effect of the shape selectivity of the catalyst is enhanced, and (3) the reaction conditions that can maintain the molar conversion of the raw material naphthalene at 30% or less are selected. In the dimethylnaphthalene produced in the step, the selectivity of the 2,3-DMN group and the 1,2-DMN group, which are difficult to convert into 2,6-DMN, can be set to 10% or less, which has been solved. It is a thing. That is, if the ratio of 2,3-DMN group and 1,2-DMN in DMN is 10% or less, 2,3-DMN group and 1,2-DMN in the product subjected to the isomerization step are DMN. The ratio in the raw material is smaller than that in the raw material. The reduced amount is easily isomerized to the 2,6-DMN group or the 2,7-DMN group, or can be distilled. Therefore, according to the present invention,
2,6-DMN can be produced at a high concentration.

As described above, in the present invention, 2,6-DMN can be obtained at a relatively high concentration, so that 2,6-DMN is obtained.
-The amount of treatment in the DMN separation step can be reduced, and separation from other DMN isomers is easy. Further, in the present invention, DM is used in the transalkylation step.
2,3-DMN group and 1,2-DM among N isomers
Since the production of N can be suppressed, the throughput of the isomerization step can be reduced. Moreover, in this isomerization step, since the treatment target is mainly the 2,6-DMN group and the 2,7-DMN group, it is possible to increase the production of 2,6-DMN under relatively mild conditions.

Further, in the present invention, since the heavy naphthalene fraction such as trialkylnaphthalene which is a problem in the conventionally proposed method for producing 2,6-DMN is hardly generated, the process efficiency is very good. Becomes

Hereinafter, each step of the present invention will be described in detail along with the flow of raw materials and products shown in FIG. [1] First step, transalkylation step: This step is a step of introducing an alkyl group into the raw material naphthalene introduced from the line 1. The alkylating agent is supplied from line 2 to this step. As the alkylating agent, polyalkylbenzenes such as xylenes, trimethylbenzenes, tetramethylbenzenes and pentamethylbenzenes are used. Of these, xylenes and trimethylbenzenes, which are highly effective in the shape selectivity of the catalyst, are preferable. Each of these may be used alone,
It is also possible to use a mixture of two or more kinds. In particular, they need not be pure, but a mixture is sufficient.

The above alkylating agent is dealkylated in the above transalkylation step and converted to benzene and toluene. Since these monocyclic aromatic compounds cannot be used as an alkylating agent, they are separated in the subsequent second distillation step and carried out from the manufacturing process. The unreacted alkylating agent is recycled through the subsequent distillation step, like the unreacted raw material naphthalene.

The transalkylation reaction can be carried out using a solid acid catalyst such as zeolites. In the present invention, a pentasil-type aluminosilicate having an excellent shape-selective effect is preferable, and particularly, JP-A-56-9211
The aluminosilicate produced by the method described in No. 4 exhibits high activity, high selectivity, and has an excellent catalyst life.
It can be preferably used. As the catalyst, it is usually preferable to use a proton-type ion-exchanged catalyst. This proton-type ion-exchanged zeolite is added to II of the periodic table.
It is also possible to use a catalyst in which one or more kinds of Group III, Group III, Group VI, and Group VII metals are supported by ion exchange or impregnation. The catalyst may be used as a single zeolite, or may be used as a matrix by mixing alumina, silica and the like.

The reaction system may be any of a normal fixed bed system, a moving bed system and a fluidized bed system, but the fixed bed system is preferred in view of simplicity.

The reaction conditions at this time are important for controlling the conversion rate of the raw material naphthalene, but if the molar conversion rate of the raw material naphthalene can be suppressed to 30% or less, it is optimum from the economical point of the process. The reaction conditions can be selected. For example, the reaction temperature is about 200 to 500 ° C,
Preferably about 300-450 ° C is suitable. The reaction pressure may be any pressure within the range of atmospheric pressure to about 100 kg / cm ² G, but usually about 10 to 40 KG / c.
A range of m ² G is suitable. The raw material is usually dissolved in an alkylating agent and sent to the catalyst bed, but the naphthalene and the alkylating agent can be sent separately. In the former case, the alkylating agent / raw material naphthalene molar ratio is usually about 1-2.
It is preferably 0 mol / mol.

The contact time of the raw material with the catalyst is an important condition for controlling the molar conversion of the raw material naphthalene to 30% or less. This contact time should be determined according to the above reaction temperature, but is usually the flow rate of the raw material with respect to the catalyst, and is about 0.
It is preferably in the range of ¹ to 5 h ⁻¹ .

The reaction can be carried out without a carrier gas, but normally a carrier gas such as hydrogen, nitrogen or steam is used. In order to prevent the deterioration of the catalyst, it is preferable to use hydrogen as a carrier gas. The amount of carrier gas with respect to the raw material is not particularly limited, but is usually about 10
It is preferable to carry out under the condition of 0 to 200 NL / mol (per naphthalene compound) (“L” represents liter, the same applies hereinafter). By carrying out transalkylation under the above conditions, the molar conversion of naphthalene compounds can be maintained at 30% or less, and thus, in DMN of 2,3-DMN group and 1,2-DMN group. The ratio to 10
It can be less than or equal to%.

The starting naphthalenes are each independently
Alternatively, it can be sent to the reactor as a mixture, and there is no particular limitation on the composition ratio thereof. The raw material naphthalene is
Naphthalenes from petroleum refineries, such as those obtained by separating and refining bottom oil of reformed oil and naphthalene in LCO,
Alternatively, those obtained by separating and refining naphthalene contained in coal tar oil from an iron mill can be used, and the properties of naphthalene are not particularly limited.

Monomethylnaphthalene in the raw material naphthalene has two kinds of isomers, but there is almost no change in the reaction results in the present invention with any of these isomers, and especially the composition ratio of these monomethylnaphthalene isomers is limited. do not have to.

Further, in order to increase the efficiency of the whole process of the present invention, naphthalene compounds separated in the separation step of the next second step can also be used as a raw material in this transalkylation step.

[2] Separation step of the second step: This step is
DM produced in the transalkylation step of the first step
It is a step of separating Ns and unreacted naphthalene.
This step also includes the step of separating the alkylating agent. These produced DMNs, unreacted naphthalene, unreacted alkylating agent and reacted alkylating agent are
It is sent from the transalkylation step of the process via line 3.

The separation of these is sufficiently carried out by using an ordinary distillation method, and this separation step is preferably carried out by a series of operations shown below. (1) Atmospheric pressure distillation step: This distillation step is a step of separating xylenes and trimethylbenzenes from the polyalkylbenzenes and returning them to the transalkylation step of the first step from the line 4. However, in the transalkylation step, it is economically disadvantageous to use benzene having no alkyl group or toluene having only one alkyl group and low reactivity as a transalkylating agent. Therefore, since benzene and toluene can be separated from xylenes and trimethylbenzenes by boiling point, they are withdrawn from the top of the distillation apparatus and discharged from the reaction system through the line 5.

(2) Vacuum distillation step: This distillation step is a step of separating unreacted naphthalene from DMN produced in the transalkylation step of the first step. The unreacted naphthalene separated in this distillation step is sent from the line 4 to the transalkylation step of the first step together with the above-mentioned xylenes and trimethylbenzenes, and used again as a raw material naphthalene. On the other hand, DMN
The compounds are sent from the line 6 to the next step 3, 2,6-DMN separation and purification step.

[3] 3,6-DMN separation and purification step of the third step: This step is a step of separating and purifying 2,6-DMN in the DMN fraction separated in the separation step of the second step. Is. As a technique for separating 2,6-DMN from the DMN fraction, various methods such as a recrystallization method and a reaction crystallization method have been proposed, and any of these methods can be used. In the present invention, in the transalkylation step of the first step, the 2,6-DMN group and 2,7-
Since the DMN group is produced, a product having a high concentration of 2,6-DMN is obtained. Therefore, the separation and purification of 2,6-DMN in the third step can be efficiently performed. The 2,6-DMN separated and purified in the third step is taken out of the system through line 7 as a product.

[4] Isomerization step of the fourth step: This step is the step of separating and purifying 2,6-DMN of the third step.
6-DMN is separated and removed, and D sent from line 8
In this step, the MN fraction is subjected to an isomerization reaction to increase the production of 2,6-DMN. In the present invention, in the transalkylation step of the first step, it is difficult to convert into a 2,6-DMN group by an isomerization reaction by maintaining the molar conversion of naphthalene as a raw material at 30% or less. Since the production of 3-DMN group and 1,2-DMN is suppressed, this isomerization step can be performed under mild reaction conditions.

The reaction system may be any of fixed bed, moving bed and fluidized bed systems similar to the transalkylation step of the first step, but if simplicity is taken into consideration,
Fixed bed method is preferred.

As the catalyst, various solid acid catalysts can be used, but in consideration of the isomerization reaction from the 2,7-DMN group to the 2,6-DMN group, it is the same as the transalkylation step of the first step. A pentasil-type aluminosilicate, particularly a pentasil-type aluminosilicate produced by the method described in JP-A-56-92114, has a reaction activity,
Good in terms of selectivity and catalyst life. Also, the first
Similar to the transalkylation step of the process, this catalyst
Usually, a proton-type ion-exchanged zeolite or a proton-type ion-exchanged zeolite is added to the periodic table II.
It is possible to use one in which one or more kinds of group III, group III, group VI, and group VII metals are supported by ion exchange or impregnation method. Further, zeolite alone may be used, or alumina, silica or the like may be used as a matrix. It may be a mixture.

A reaction temperature of about 200 to 500 ° C., preferably about 300 to 400 ° C. is suitable for giving a high yield and high selectivity. The reaction pressure is from normal pressure to about 10
0 kg / cm ² G, preferably normal pressure to about 30 kg / cm
It is in the range of ² G. The oil passing rate of the raw material is LHSV, and the oil passing amount of DMN is about 0.1 to 10 with respect to the catalyst.
Suitably, it is in the range of h ⁻¹ , preferably 0.1 to ¹ h ⁻¹ .

A solvent may or may not be used during the isomerization reaction of DMNs. When used, benzene, monocyclic aromatic compounds such as toluene,
Naphthenic hydrocarbons such as cyclohexane and methylcyclohexane, paraffinic hydrocarbons such as C5, C6 and C7 can be used.

The presence or absence of the carrier gas does not affect the initial isomerization activity so much, but considering the prolongation of the catalyst life, it is preferable to use hydrogen as the carrier gas. Usually, the amount of hydrogen gas is preferably about 100 to 200 NL / mol with respect to the DMN as a raw material.

The products in this isomerization step (mainly 2,6-DMN, but also containing other DMNs and naphthalenes) are sent from the line 9 to the separation step of the second step, and again, Subjected to distillation separation.

[0041]

【Example】

(1) Synthesis of Zeolite In an autoclave, 1605 g of colloidal silica (silica content 20.6 wt%), 500 g of pure water and 362 g of diglycolamine were added to a solution of caustic soda 3
An aqueous solution prepared by dissolving 0.6 g in 500 g of pure water and an aqueous solution prepared by dissolving 31.6 g of sodium aluminate in 493 g of pure water were added while stirring at a speed of 250 rpm,
The gel raw material was prepared. In the autoclave,
The mixture was kept at 140 ° C. for 20 hours while being stirred at a speed of 250 rpm. Then 250 rpm in the autoclave
The mixture was kept at 160 ° C. for 48 hours while being stirred at the speed of 1. The obtained crystal product was filtered and washed with pure water until the pH of the filtrate became 8 or less to obtain a highly crystalline aluminosilicate zeolite. The highly crystalline aluminosilicate zeolite was washed thoroughly with water and then washed in an electric dryer at 110 ° C for 3 hours.
Dried for hours.

The highly crystalline aluminosilicate zeolite synthesized as described above (hereinafter, "DGA zeolite")
The ratio of SiO ₂ / Al ₂ O ₃ was 40. The DGA zeolite was a zeolite having a pentasil type structure. Further, as ZSM-5 zeolite, a commercially available zeolite having the same SiO ₂ / Al ₂ O ₃ ratio of 40 was prepared.

(2) Conversion to Proton-Type Zeolite The DGA zeolite synthesized as described above is used in an aqueous 4N ammonium chloride solution at a ratio of 5 g per 1 g of the zeolite, and the solution is placed in the aqueous solution at 90 ° C. for 2 hours. Ion exchange was performed. This ion exchange operation was repeated 3 times. After the ion exchange, the zeolite was washed with pure water until chlorine was not detected, and dried in an electric dryer at 110 ° C. for 3 hours. Then, in an electric firing furnace in the presence of air,
It was calcined at 540 ° C. for 3 hours to obtain a proton-type DGA zeolite. In the same operation, the above ZSM-5 zeolite and a commercially available Y-type zeolite (SiO ₂ /
Al ₂ O ₃ ratio 5.0) was made into a proton type and used as a catalyst.

(3) Transalkylation Step of First Step Examples 1 to 7 and Comparative Examples 1 to 3 Proton-type DGA zeolite, ZSM-5 zeolite, and Y-type zeolite obtained by the above-mentioned catalyst preparation method were used. ,
5m of 16-28 mesh prepared by pressure molding
Three L reaction tubes each having an inner diameter of 15 mm and made of stainless steel were filled in each of them, and transalkylation reaction was carried out under various conditions. Raw materials are naphthalene, 1-methylnaphthalene,
2-Methylnaphthalene (all use special grade products manufactured by Wako Pure Chemical Industries, Ltd.) at various ratios shown in Tables 1, 3 and 5 (all use special grade reagents manufactured by Kanto Chemical Co., Inc.) What was melt | dissolved in was used. When methanol was used as the alkylating agent, the raw material naphthalene was dissolved in benzene (using a special grade reagent manufactured by Kanto Kagaku Co., Ltd.), and a predetermined amount of methanol was added thereto to be used as the raw material. The above results are shown in Tables 2, 4 and 6.

[0045]

[Table 1]

The symbols in Table 1 indicate that H / DGA is a proton-type DGA zeolite, the AL agent is an alkylating agent, and the TM agent is TM.
B is trimethylbenzene, XYL is xylene, Np
Means naphthalene, and the same abbreviations are used in the following tables.

[0047]

[Table 2]

The symbols in Table 2 are BEZN and benzene,
TL means toluene, TEMB means tetramethylbenzene, MMN means monomethylnaphthalene, EN means ethylnaphthalene, TMN means trimethylnaphthalene,
The same abbreviations are used in the tables below.

[0049]

[Table 3]

H / ZSM in Table 3 means a proton type ZSM zeolite, and is the same in the following tables.

[0051]

[Table 4]

Numerical values in parentheses of the Np type product distribution in Table 4 indicate mol%, and the same applies to the following tables.

[0053]

[Table 5]

In Table 5, H / Y means proton-type Y-type zeolite and MeOH means methanol, which are the same in the following tables.

[0055]

[Table 6]

As is clear from Tables 2, 4 and 6, in Examples 1 to 7, if the molar conversion of the raw material naphthalene can be kept at 30% or less under any reaction conditions, the formation 2,3-DMN group in DMN, 1,
The generation ratio of the 2-DMN group can be 10% or less. On the other hand, in Comparative Example 1 in which the molar conversion ratio of the raw material naphthalene exceeds 30%, Comparative Example 2 in which methanol is used as the alkylating agent, and Comparative Example 3 in which Y-type zeolite having a poor shape-selective action is used as a catalyst. , 2,3-
The DMN group generation rate exceeds 20%. Therefore, the scope of the present invention as shown in Examples 1 to 7 is
2,6-DMN group and 2,7-D with high selectivity
It can be seen that this is a condition for creating an MN group. Note that 1,2-DMN was not produced under the reaction conditions as shown in Examples 1-7.

The effect of the present invention in the above transalkylation step becomes more apparent by examining the isomerization reactivity of DMNs. (4) Isomerization Step of Fourth Step Examples 8 and 9, Comparative Example 4 In the same manner as in the transalkylation step of (3) above,
The isomerization process was performed under the reaction conditions shown in Table 7. In order to clarify the difference in isomerization reactivity of the catalyst depending on the composition of each raw material, the reagent DMNs (using a special grade manufactured by Wako Pure Chemical Industries, Ltd.) were used as raw materials, and these were benzene (Wako Pure Chemical Industries, Ltd.). And used for the reaction. The composition of the raw material was based on the composition of DMN obtained in the transalkylation step of (3) above, with 2,6-DMN being 80
Each composition was determined assuming recovery in% yield and is shown in Tables 8-10. In addition, 1,7-DMN is not sold as a reagent product, and 2,7-DMN is not available as 1,7-D
A raw material was prepared by further adding only the MN concentration. Example 8 is Example 1 of the transalkylation step of (3) above.
Example 9 is the same as Example 7 of the transalkylation step.
Comparative Example 4 is a comparative example 1 of the transalkylation step.
, Respectively. The isomerization reaction conditions and results are shown in Tables 8 to 10.

[0058]

[Table 7]

[0059]

[Table 8]

In Table 8, EB means ethylbenzene,
2,3-Gr. The reduction rate and the EN reduction rate are obtained by the equation (3). The same applies in the table below.

[0061]

[Equation 3]

[0062]

[Table 9]

As is clear from Tables 8 and 9, in the transalkylation step, 1,2-DMN group, 2,
When the proportion of 3-DMN group in DMN is 10% or less, it is relatively dealkylated or 2,6-DMN
It can be seen that the isomerization reaction into a group or a 2,7-DMN group is likely to occur, and the concentration of the 2,3-DMN group decreases as compared to the raw material. On the other hand, 2,3-DMN
In Comparative Example 4 in which the group contained 20% or more, the concentration of the 2,3-DMN group in the isomerization product was rather increased, which means that the concentration of 2,3-DMN in the production process was 2,3-.
It shows that the DMN group accumulates in the system, which lowers the efficiency of the manufacturing process and ultimately deteriorates the economical efficiency of the manufacturing process.

(5) All Reaction Steps Example 10 (5,1) Preparation of Raw Material As a raw material for the transalkylation step, naphthalene 5 was used.
0.0 g, 25.0 g of 1-methylnaphthalene, and 25.0 g of 2-methylnaphthalene were dissolved in 400 g of an alkylating agent. The alkylating agent is m-xylene 23.7 wt.
%, P-xylene 13.2 wt%, o-xylene 13.
1wt%, 1,3,5-trimethylbenzene 25.0w
t%, 1,2,4-trimethylbenzene 25.0 wt%
The compositional ratio of was prepared and used.

(5, 2) First Step (Transalkylation Step) As a catalyst, 10 g of the above proton-type DGA zeolite prepared by pressure molding into 16 to 28 mesh was prepared.
It was filled in a stainless steel reaction tube having an inner diameter of 15 mm, and the reaction temperature was 400 ° C., the reaction pressure was 10 kg / cm ² G, WHSV (per material naphthalene) 0.77 h ⁻¹ , H ₂ / total material ratio 240 NL / L, The above raw material was oiled for 13 hours. As a result, 485 g of product oil was obtained.

When the composition of the produced oil was analyzed, it was found that (benzene + toluene) 3.4 wt%, (xylenes + trimethylbenzenes) 75.8 wt%, (tetramethylbenzenes) 0.1 wt%, (naphthalenes). ) 8.0 wt%
(41.9 mol%), (monomethylnaphthalenes) 8.
2 wt% (38.7 mol%), (DMNs) 4.2 wt
% (18.1 mol%), (ethylnaphthalene) 0.3
wt% (1.3 mol%), (trimethylphthalenes) 0
It was wt% (0 mol%). The molar conversion rate of the raw material naphthalene was 19.4%.

The composition of DMNs is 2,6-DMN26.
3%, 1,6-DMN18.0%, 1,5-DMN4.
7% (total of 2,6-DMN groups is 49.0%),
2,7-DMN 29.0%, 1,7-DMN 18.0%
(47.0% in total of 2,7-DMN group), 2,
It was 4.0% of 3-DMN.

(5, 3) Second step (distillation step) 485 g of the product oil of the transalkylation step was subjected to a reflux ratio of 15 using a 45-stage Oldershaw distillation apparatus.
It was divided into the following boiling range fractions. For distillates above naphthalene, the distillation was carried out under a reduced pressure of 10 mmHg. (1) 80 to 110 ° C .; benzene, toluene fraction (2) 136 to 176 ° C .; xylene, trimethylbenzenes (3) 217 to 248 ° C .; naphthalene, monomethylnaphthalene, and some tetramethylbenzenes (4) 250-270 ° C; ethylnaphthalene, DMN
The yield of each fraction is (1) 16.5g, (2)
Is 367.6 g, (3) is 63.3 g, and (4) is 17.
It was 4 g.

(5, 4) Third Step (2,6-DMN Separation and Purification Step) 100 mL of the ethylnaphthalene and DMN fraction 17.4 g of (4) obtained in the second step (distillation step) are added. Then, 26.0 g of toluene was added to the eggplant-shaped flask to dissolve naphthalene. After heating the flask to 90 ° C., 13.8 g of metanitrobenzoic acid was added and dissolved. After stirring for 30 minutes, the reaction mixture was cooled to room temperature, and 2,6-DMN-metanitrobenzoic acid reaction crystallization product was deposited.

The solid-liquid mixture of the above crystallized product and DMN was separated by filtration to obtain 18.1 g of a crystallized product. The crystallized product was decomposed with n-heptane, and a DMN fraction rich in 2,6-DMN was recovered as an n-heptane solution. The solvent was separated from the n-heptane solution by an evaporator to give a solid 4.
3 g was obtained. When the composition of this solid was analyzed,
70.2 wt% (3.1 g) of 2,6-DMN was contained. In addition, the filtrate after separating the crystallized product was treated with 1N NaOH.
After washing with an aqueous solution to remove the dissolved metanitrobenzoic acid, toluene was separated with an evaporator,
13.1 g of DMN distillate solid matter of poor 2,6-DMN was obtained. The composition of this solid is 2,6-DMN 8.9 wt.
%, 1,6-DMN 21.2 wt%, 1,5-DMN
6.7 wt%, 2,7-DMN26.8 wt%, 1,7
-DMN 21.2 wt%, 2,3-DMN 6.7 wt
%, And ethylnaphthalenes were 8.5 wt%.

(5, 5) Fourth step (isomerization step) Solid DMN fraction of solid 2,6-DMN as described above 13.1
35 g of benzene was added to g to prepare an isomerization step raw material. The same catalyst used in the first step as a catalyst 5
g in a stainless steel reaction tube having an inner diameter of 15 mm, reaction temperature 350 ° C., reaction pressure 10 kg / cm ² G, WHS
V (per raw material naphthalene) 0.26 h ⁻¹ , H ₂ /
Under the condition that the total raw material ratio is 300 NL / L,
Oiled for 0 hours. As a result, 47.9 g of oil was obtained.
Benzene is separated from this oil by an evaporator,
13.0 g of isomerization reaction product was obtained. The composition of this reaction product is as follows: 7.2 wt% naphthalene, 3.8 wt% monomethylnaphthalenes, 1.3 wt% ethylnaphthalenes.
%, DMNs 87.7 wt%. Further, the isomer composition of DMNs is 2,6-DMN22.0 wt%, 1,
6-DMN20.7wt%, 1,5-DMN2.3wt
%, 2,7-DMN25.7 wt%, 1,7-DMN2
3.5 wt%, 2,3-DMN 1.3 wt%, 1,3-
DMN was 3.0 wt% and 1,4-DMN was 1.5 wt%.

2,6-DMN was separated from the above-mentioned isomerization reaction product by the same operation as in the third step of (5,4), and a 2,6-DMN-metanitrobenzoic acid reaction crystallization product was obtained. Was obtained in an amount of 2.5 g, and the crystallized product contained 1.8 g of 2,6-DMN. In addition, the ethylnaphthalene and 2,3-DMN groups, which are problematic at the time of recycling, have decreased 1.1 g to 0.2 g and 0.9 g to 0.5 g, respectively, which is one of the objects of the present invention. It was found that the accumulation of by-products in the process can be avoided. These results are the results of performing only one cycle and are 10
Total of 5.6 g of 2,6-D from 0 g of naphthalene raw material
The MN was manufactured and recovered.

[0073]

As described in detail above, according to the present invention, the first
In the transalkylation step of the step, by suppressing the molar conversion of the raw material naphthalene to 30% or less,
10% production of DMNs difficult to isomerize to 2,6-DMN
The following can be suppressed. As a result, in the present invention, in the separation step of the second and third steps and the separation and purification step of 2,6-DMN, 2,6-DMN can be efficiently separated and recovered, and the isomerization of the fourth step is performed. In the process, 2,6-DMN can be obtained with high efficiency.
Therefore, according to the present invention, industrialization of 2,6-DMN production, which has hitherto been unattainable, can be easily achieved.

[Brief description of drawings]

FIG. 1 is a diagram showing each step of the present invention and a flow of raw materials and products in the step.

[Procedure amendment]

[Submission date] May 9, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction content]

The symbols in Table 2 are BEZN and benzene,
TL means toluene, TEMB means tetramethylbenzene, MMN means monomethylnaphthalene, EN means ethylnaphthalene, TMN means trimethylnaphthalene,
The same abbreviations are used in the tables below. Well
In addition, the numerical value in parentheses of the Np type production distribution in Table 2 is mol%
Is shown.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0051

[Correction method] Change

[Correction content]

[0051]

[Table 4]

Claims (1)

[Claims] 1. [1] Using naphthalene or monomethylnaphthalene or a mixture thereof as a raw material, in the presence of a pentasil-type zeolite, the polyalkylbenzene is used to adjust the molar conversion of the raw material represented by the formula 1 to 3
The first step of producing dimethylnaphthalene by transalkylation to 0% or less, [2] The reaction mixture of the first step is a non-reusable polyalkylbenzene, a reusable polyalkylbenzene, unreacted naphthalene, monomethylnaphthalene,
Second step for separating dimethylnaphthalene into 4 fractions, [3] Third step for separating 2,6-dimethylnaphthalene from dimethylnaphthalene in the fraction separated in the second step
Step, and [4] a fourth step of producing 2,6-dimethylnaphthalene by isomerizing dimethylnaphthalene after separating 2,6-dimethylnaphthalene in the third step, A method for producing 6-dimethylnaphthalene.